1. Field of the Invention
The present invention relates to an apparatus for purification of water from organic halides contained therein improved so as to achieve an efficiency as close as to the ideal level of perfect purification which has conventionally never been attained.
Indeed, the invention allows a concentration of residual organic halides contained in water to be decreased to the order of p p b.
2. Prior Art
Conventionally, the active carbon adsorption process and the porous particle adsorption process have been utilized for purification of water from organic halides contained therein. While these processes have been effective to decrease a concentration of the residual organic halides to the order of p p m, it has been difficult for these processes to decrease the residual concentration to the order lower than said p p m. In addition, organic halides generally present a chemical stability which is too high to be easily decomposed by microorganisms.
It is also known to utilize volatility of organic halides for purification of water and, according to this process, organic halides are forcibly evaporated by dispersing air bubbles into water.
While organic halides are very useful substances for various industries, they may always adversely affect our environment and therefore strict standards have been prescribed with respect to handling of these substances. Specifically, the presence of these substances in water even at a concentration as low as in the order of p p b is considered to affect the ecosystem. Consequently, the foul water quality standard reading "should not be detected" has been prescribed. Expression "should not be detected" can be construed, in view of the detection limit of the presently available analyzers, as 10 p p b. This value is extremely small and even a slight quantity of organic halides contained in foul water may exceed the standardized limit value. Accordingly, these standard really aim to prohibit any use of organic halides.
To decompose organic halides resistant to decomposition by microorganism, active carbon and porous particles have conventionally been utilized to adsorb these organic halides thereon. However, an adsorption efficiency achieved by the process utilizing porous particles is limited by the phenomenon of adsorption equilibrium, i.e., a rate of adsorption for organic halides remains in equilibrium with a rate of desorption for organic halides so long as their concentrations are less than a predetermined level. With a consequence, this porous particle adsorption process is limited in its effect of decreasing the organic halide concentration. While the other impurities contained in water can be disposed without any problem because the standard concentrations prescribed for most of them are substantially higher than said equilibrium concentration, it is practically difficult for organic halides to be completely disposed because the equilibrium concentration is higher than the standard concentration prescribed for organic halides.
Dispersion air bubble into water containing these organic halides causes the organic halides to be evaporated into said air bubbles and then to be diffused into the outer air. As a result, the concentration of the organic halides in water can be thereby decreased. Certainly, this process can decrease the concentration to a level lower than the level achieved by the conventional active carbon adsorption process. However, this is a less recommendable process, because the organic halides thus diffused into the outer air may often cause another environmental pollution.
In spite of the strict regulation standards for organic halides, pollution of respective hydrospheres has steadily become serious and widespread even to sources of respective waterworks. Presently, the waterworks law includes no distinct regulation concerning the organic halides. Should the source of water supply be polluted by organic halides, polluted water would be supplied to general households because perfect removal of the organic halides is difficult. Eventually, foul water from the household would exceed the standardized concentration value. Presently, the only measure possibly taken to avoid such environmental pollution due to organic halides is "to avoid the use of organic halides". However, it is practically impossible to fully prohibit use of organic halides, since these organic halides are industrially important substances. Accordingly, there is always a serious demand for satisfactory purification of water already polluted by organic halides.